The present invention relates to a heat exchanger made of aluminum alloys, such as condenser, evaporator and so forth incorporated in automobile air conditioners, and more particularly relates to a corrugate fin type heat exchanger made of aluminum alloys and improved to prevent pitting corrosion of the heat exchanger tubes, and further relates to a tube material for such heat exchanger.
Conventionally, the tubes of corrugate fin type heat exchangers made of aluminum alloys are formed of an aluminum alloy generally referred to as 3003 specified in the U.S. Aluminum Association Standard (hereinafter called "AA") having compositions consisting essentially of 0.05 to 0.20 wt% of Cu, not more than 0.6 wt% of Si, not more than 0.7 wt% of Fe, 1.0 to 1.5 wt% of Mn, not more than 0.10 wt% of Zn and the balance Al, or are formed of an aluminum alloy of compositions having a slightly lower Mn content than the AA 3003 aluminum alloy. As to the material of the corrugate fin, a core material of an aluminum-zinc alloy, which has an electrochemical potential lower than the AA 3003 aluminum alloy constituting the tubes and thus exhibits a sacrificial corrosion effect to prevent the corrosion of the tubes, is used in combination with a cladding layer for brazing filler alloy.
The AA 3003 aluminum alloy used as the tube material, however, has such poor drawing or hot-extrusion characteristics (drawability or hot-extrudability) as amounts, for example, to about 1/3 of that of pure aluminum such as AA 1050. Therefore, the production of the heat exchanger tubes from the AA 3003 alloy by drawing or hot-extrusion costs much higher than the production from the pure aluminum, resulting in a raised cost of production of the heat exchanger as a whole.